1. Field of the Invention
The present invention relates to prosthetic meshes and their methods of manufacture.
2. Description of the Related Art
The prior art includes a prosthetic mesh made of an implantable, non-resorbable, flexible material, designed to be implanted for the parietal repair of hernias and eventrations of the abdominal wall. These meshes, which are usually made of implantable polypropylene, preferably have tight mesh openings and are obtained by knitting, welding or weaving. They are supplied to surgeons pre-cut, in the form of a flat element. However, this flat element must be applied to a concave surface by the surgeon. As a result of the difference in conformation, the mesh is difficult to put into position, especially since one of its relatively broad margins has to be slipped between the parietal peritoneium and the abdominopelvic wall. Moreover, as it is being put in place, the mesh folds or wrinkles and is hard to keep in place at the point where many surgeons prefer to attach it. Its inner margin corresponding to the other small side must be slipped between the bladder and the abdominopelvic wall. A straight margin is poorly suited for insertion of the internal edge.
The invention palliates these disadvantages by means of a mesh which is easier to put in place and which, once in position, has virtually no tendency to shift, without the need for any additional intervention such as fixation, thereby making it possible to reinforce all the weak points of the inguinofemoral region, resulting in a much lower failure rate than heretofore.
According to the invention, the mesh assumes a curved shape of itself.
Due to this natural curvature which is imparted to it during fabrication and which can match the concavity on which it is to be placed, on being put into place by the surgeon the mesh conforms to the anatomic shapes, and it has no tendency to shift because it is not subjected to strain due to its deformation. By preference, the mesh, while being capable of the temporary deformation necessary for it to be put in place, should have a sufficient tendency to resume its initial curved shape, without deviating therefrom, so that it does not fold or wrinkle under the pressure of the viscera. The preferred mesh resumes its approximate original shape after a single temporary deformation. To obtain this effect more easily, it is desirable for the margins of the mesh to be more rigid than the rest of the mesh, for example by fusing of the material marginally over a width of at least 5 mm. The margins are preferably smooth, to keep the mesh from catching as it is being positioned.
To facilitate insertion, it is preferred that the mesh have, not an external side, but a roughly tapered end by which it can be slipped more easily between the parietal peritoneum and the abdominopelvic wall. It is also preferred that its inner margin, the farthest from that end, be incurvated, especially in its outer portion, roughly according to a circle permitting the repositioning of the bladder after the mesh has been put in place.
For optimum fitting of the mesh to the areas requiring reinforcement, the mesh can have a double convexity in two perpendicular planes.
According to one embodiment, this mesh is composed of a part in the form of a spherical cap extending from the inner margin to beyond the location where the strongest reinforcement is desired, prolonged by a conical part which, at its end, defines the outer tip. The radius of the spherical part can be between 80 and 120 mm. The largest dimension of the mesh can be between 120 and 150 mm, while the dimension perpendicular to this largest dimension can be between 70 and 100 mm.
In order for the mesh to fit optimally into the pelvic area, a rounded edge is provided between the spherical cap and the cone on one hand, and a lower part with a large radius of curvature, which has a depression near its center. This depression is designed to be placed opposite the external iliac vessels, while the rounded edge is designed to be placed within the axis of the inguinal ligament.
A further object of the invention is a method of manufacture of a mesh according to the invention, which consists in placing a flat piece of an implantable, non-resorbable, flexible material in a curved template and bringing this piece to a sufficient temperature for a sufficient period of time so that it retains a curved shape, even after cooling, and upon removal from the template.
A final object of the invention is a package for a mesh, which comprises a body in which a cover nests, characterized in that the upper surface of the bottom of the body is derived from a template which, together with a concave part of the same shape provided on the lower surface of the cover, defines a receptacle for the curved mesh.